Elementary physics
__TOC__ Elementary physics :Highly recommend: ::Thinking Physics Is Gedanken Physics by Lewis Carroll Epstein ::Understanding physics by Isaac Asimov Physics is all calculus. Trying to do physics without calculus is like trying to run a race on one leg. If the position of an object as a function of time is given by :: position = p(t) then the velocity is given by :: v = \frac{dp}{dt} and the acceleration is given by :: a = \frac{dv}{dt} = \frac{d^2p}{dt^2} Velocity has units of distance per time (like miles per hour). Acceleration has units of distance per time per time. The momentum of an object is equal to the mass times the velocity :: Momentum = m v The kinetic energy of an object is equal to half the mass times the velocity squared :: E = \frac{m v^2}{2} In the image below a red object of unit mass moving with velocity 2 strikes a blue stationary object with equal mass. The total horizontal momentum, total vertical momentum, and total energy are unchanged by the collision. In other words, energy and momentum are . A force of 1 Newton acting continuously on a mass of 1 kg will cause that mass to accelerate at 1 m/s2 :: F = m a :After the object has moved a distance of 2 meters it will have gained a kinetic energy of :: E = F \cdot distance = 1 \, Newton \cdot 2 \, meters = 2 \, Joules Gravity on Earth causes all free falling objects to accelerate downward at 9.8 m/s2 Back to top Atoms :External link: Periodic table at ptable.com A red circle is an unpaired electron in the outermost shell. A blue circle is a of electrons. Each electron shell is twice the radius of the previous shell. Copper is whats known as a . Zinc has a very low boiling point. |} Silver is whats known as a . Cadmium has a very low boiling point. |} Gold is whats known as a . Mercury has a very low boiling point. |} |} Note: The metallic forms of the elements have electronic structures that differ slightly from the one the predicts. Each unpaired electron in the outermost shell (called the valence shell) forms a with an unpaired electron in the outermost shell of a neighboring atom. Pure gas consists of . : (H2), (F2), (Cl2), (Br2), and (I2) all form . So does (N2) and (O2). Atoms that have no unpaired electrons in their valence shell are called . Noble gases do not form chemical bonds and are therefore . (He), (Ne), (Ar), (Kr), (Xe), and (Rn) are noble gases. : A single molecule of consists of one Fluorine atom and one hydrogen atom and is therefore diatomic. Fluorine is a powerful . In fact, Fluorine is the most element known. (It really likes electrons). Fluorine is much more electronegative than hydrogen. This causes Hydrogen Fluoride to be a . :: A single molecule of (H2O) consists of one oxygen atom and two hydrogen atoms. Water is a polar molecule. :: A single molecule of (NH3) consists of one nitrogen atom and three hydrogen atoms. Ammonia is a polar molecule. :: A single molecule of (CH4) consists of one carbon atom and four hydrogen atoms. Methane is a hydrocarbon. Hydrocarbons are non-polar molecules and therefore not soluble in water. Methane is a gas. It boils at -161 °C. :: A single molecule of (C2H6) consists of two carbon atoms and six hydrogen atoms. Ethane is a gas. It boils at -88 °C. :: A single molecule of (C2H6O), also known as drinking alcohol, consists of two carbon atoms, six hydrogen atoms, and one oxygen atom. . :: A single molecule of (C8H18) consists of eight carbon atoms and eighteen hydrogen atoms. Octane is a liquid. It boils at 125 °C. If the chain were even longer and the hydrogen atoms were replaced with fluorine atoms then you would have . :: But Benzene is a little bit different. A single molecule of consists of six carbon atoms and six hydrogen atoms arranged in a ring. Each carbon atom bonds with 2 other carbon atoms and with one hydrogen atom thus accounting for three unpaired electrons per carbon atom. But, as we already know, each carbon atom has four unpaired electrons so one electron per carbon atom is unaccounted for. There are six carbon atoms therefore a total of six electrons per benzene molecule are unaccounted for. Those six form the blue circle around the molecule. See also: , , and . Benzene molecules are shaped like flat plates. (See .) :: A single molecule of consists of five carbon atoms, five hydrogen atoms, and one nitrogen atom arranged in a ring. Six unpaired electrons form the blue ring around the molecule. Pyridine is a nitrogen . :: consists of carbon atoms densely packed in a regular hexagonal pattern: :: consist of a two-dimensional hexagonal lattice of carbon atoms, bent and joined in one direction so as to form a hollow cylinder: :: A single molecule of is a of carbon atoms: :: is a : :: :Its Boron atom has a vacant orbital which can form a covalent bond by sharing a lone pair of electrons on an atom in a base (in this case ammonia):Wikipedia:Acid :: A molecule of consists of one Antimony atom and five Fluorine atoms. :: :Its Antimony atom has a vacant orbital which can form a covalent bond by sharing a lone pair of electrons with a sixth Fluorine atom (actually its an ion) thus creating Antimony hexafluoride. :: Note that the molecule in the image above has a net negative charge of -1. I would guess that the reason the six pairs of electrons are able to share the outer electron shell in antimony is because of sd5 . Antimony hexafluoride form a with ions creating which is the strongest known with =-28. :Thats 1016 times stronger than 100% which has H0=-12. It has been shown to even hydrocarbons (which cannot normally be "protonated"). It can only be stored in containers lined with Teflon. From Wikipedia:Grotthuss mechanism: Proton jumping is the process by which an 'excess' proton diffuses through the network of water molecules or other hydrogen-bonded liquids through the formation and concomitant cleavage of covalent bonds involving neighboring molecules. The details of the hopping and transport mechanism are still debated. Back to top References